When the dagger appeared, it showed the audience, even though they already knew, that what Macbeth was about to do was evil. The witches prophecy was supposed to be good for Macbeth, but ultimately it was what led to his downfall, so it turned out to be evil. The apparitions that appeared in front of Macbeth to tell him about Macduff, the Woods, and that no man born of woman could kill him where used to make the mood of that scene seem ominous and unsettling.
The supernatural occurrences in Macbeth all played a very important role in the story. Whether they were used to set the mood of the particular scene, represent a thought or emotion that the character felt, or to move the plot along; each event had a big impact on the story including the witches, the dagger, the prophecies, and the